The use of fiberglass to produce insulation products, such as automobile headliners and room dividers, is known. In general, a binder is prepared from a suitable material, such as phenol-formaldehyde resole resins, and this binder is applied to a glass fiber base material. The binder-coated base material later can be shaped, sized as desired, and cured to maintain the base material in this final, desired shape.
Many patents and other documents describe general fiberglass production processes. U.S. Pat. No. 5,952,440 contains a detailed description of the history and the state of the art relating to this type of fiberglass technology. This patent is entirely incorporated herein by reference.
In general, phenol-formaldehyde resole resins have been used in preparing binders for fiberglass insulation products. These resins have a disadvantage, however, in that they generally contain a large amount of free formaldehyde, which must be eliminated prior to applying the binder to the fiberglass product. Formaldehyde scavengers typically are used to remove this free formaldehyde from a phenol-formaldehyde resole resin.
Urea is one commonly used formaldehyde scavenger. While urea is relatively inexpensive as compared to some other formaldehyde scavengers, its use as a scavenger is not ideal in producing at least some fiberglass insulation products. When urea reacts with formaldehyde, a formaldehyde-amine species is formed. When this species breaks down (e.g., thermal breakdown), trimethylamine (TMA) is produced and released from the finished fiberglass product. TMA has a distinctive and unpleasant odor (a “fishy” odor), and therefore, its formation should be avoided in at least some fiberglass products.
In order to minimize odors generated from use of urea as a formaldehyde scavenger, fiberglass producers have generally taken two approaches. First, they allow the phenol-formaldehyde resole resin reaction procedure to proceed until there is a very low free formaldehyde content in the resin product, which minimizes the amount of scavenger needed to react with the remaining free formaldehyde. Second, they add more thermally stable formaldehyde scavengers (such as melamine) to the binder in an effort to minimize TMA production during binder cure.
U.S. Pat. No. 5,952,440 describes a system that attempts to take advantage of both of these possible “cures.” Specifically, when producing the resole resin in the system described in U.S. Pat. No. 5,952,440, the phenol-formaldehyde reaction is allowed to proceed until the free formaldehyde content in the resin is in the range of 0.5% to 2.5%, by weight (based on a total weight of the resin), and preferably between 0.7 and 2% by weight, and most advantageously between 0.8 and 1.2% by weight. Then, melamine is added to the resin to react with the remaining free formaldehyde (melamine acts as a formaldehyde “scavenger”).
These “cures,” however, are not without their own associated drawbacks and disadvantages. For example, allowing the resole resin to react for a sufficient time to reach a very low free formaldehyde content will result in a resin product having a higher molecular weight (the resin is said to be more “advanced”). High molecular weight phenol-formaldehyde resole resins tend to be sticky, which causes the binder and the binder-coated fiberglass product to stick to the production equipment, particularly in the fiberglass forming chamber. Additionally, higher molecular weight phenol-formaldehyde resole resins tend to have a higher tetradimer content. “Tetradimer” is a phenol-formaldehyde dimer present in all phenolic resoles. This dimer is very crystalline and precipitates readily, especially when the free formaldehyde of the resin has been scavenged, for example, by melamine or urea. Tetradimer precipitation has long been recognized in the industry as a problem that can result, for example, in plugged spray nozzles and in precipitate formation in the resin, premix, and binder storage tanks. This precipitate must be removed and discarded, which increases production expenses and decreases binder efficiency.
Use of a large amount of melamine as a formaldehyde scavenger, as described in U.S. Pat. No. 5,952,440, also can lead to precipitation problems. U.S. Pat. No. 5,952,440 describes use of melamine such that the molar ratio of free formaldehyde to melamine is 0.5 to 1.5. Melamine is known to have limited water solubility. Therefore, it may be necessary to filter out excess, undissolved melamine, as described in U.S. Pat. No. 5,952,440. This is an expensive and time-consuming additional step. Moreover, when used as a formaldehyde scavenger, melamine reacts with formaldehyde to form methylolated melamine species, which have been shown to be unstable. This methylolated melamine can form an undesirable white precipitate when the resin is allowed to age. Additionally, melamine is fairly expensive, which increases the cost of the resulting fiberglass products.
U.S. Pat. No. 3,819,441 describes a process for making glass fiber products using phenolic binder resins that are condensed to an advanced stage such that the condensate is water-insoluble at a pH of 7.5. The condensate is solubilized by adding a small amount of a non-ionic or anionic agent (such as coconut fatty acid amine). During production of the binder in the process described in this patent, melamine and a large relative amount of urea are added to the binder mixture. This patent is entirely incorporated herein by reference. Because of its relatively high urea content, it is expected that this material would produce a significantly unpleasant odor.
Several U.S. patents describe use of an acidic binder where the formaldehyde is scavenged with melamine to produce a low odor/low TMA emission fiberglass product. See, for example, U.S. Pat. Nos. 5,296,584, 5,358,748, 5,368,803, and 5,505,998, which patents are entirely incorporated herein by reference. Such acidic binders, however, are very corrosive. Fiberglass plants that use such binders must have stainless steel equipment at any place that has direct contact with the binder. Stainless steel has not traditionally been used in fiberglass plants. Therefore, use of these patented systems may require that the plants “retrofit” with stainless steel, at considerable cost in both money and down time. Additionally, acidic binders are relatively unstable and tend to lose their water dilutability rather quickly. This can produce precipitates in the binder material and require that the binder be filtered and/or discarded.
Other known resin/binder systems are emulsifiable rather than water soluble. Emulsifiable systems, however, are more difficult for fiberglass manufacturers to handle because if the emulsion breaks, high molecular weight resin will coat the equipment. Additionally, emulsifiable resins and binders typically have a higher molecular weight than their water-soluble counterparts. Therefore, even if the emulsions remain stable and do not break, sticking problems can result, as generally described above.
The present invention has been developed to address various disadvantages and problems known in this art. This invention relates to water soluble, low molecular weight products (e.g., phenol-formaldehyde resin-containing binders) that can be used, for example, in the production of fiberglass products, as well as to methods for making the binders and fiberglass products. These products and methods also may be used, for example, in making low odor fiberglass products.